body{
    margin: 0;
    padding: 0;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: #0b1522;
}
a{
    position: relative;
    display: inline-block;
    width: 200px;
    height: 60px;
    color: #fff;
    line-height: 60px;
    text-align: center;
    text-decoration: none;
    background: skyblue linear-gradient(90deg,
    #03a9f4,
    #f441a5,
    #ffeb3d,
    #03a9f4);
    background-size: 400%;
    border-radius: 10px;
}
@keyframes animate {
    0%{
        background-position: 0 0;
    }
    100%{
        background-position: 400% 0;
    }
}
a:hover{
    animation: animate 8s linear infinite;
}
a:before{
    content: '';
    position: absolute;
    left: -5px;
    top: -5px;
    right: -5px;
    bottom: -5px;
    z-index: -1;
    background: linear-gradient(90deg,
    #03a9f4,
    #f441a5,
    #ffeb3d,
    #03a9f4);
    background-size: 400%;
    border-radius: 10px;
    opacity: 0;
    transition: all 1s;
}
a:hover:before{
    filter: blur(20px);
    opacity: 1;
}